The invention relates to packaged albuterol formulations having a long shelf life.
An attractive method for aseptic packaging of sterile pharmaceutical solutions is an automated process called blow-fill-seal (BFS) technology, wherein plastic containers are formed, filled and sealed in one continuous operation with limited need for human intervention. An advantage of this technology is that the opportunity for microbial contamination is minimized. It has been used for the production of unit dosage vials containing albuterol.
Albuterol is an optically active compound which can exist as an (R)- or an (S)-enantiomer, or as a mixture of the two enantiomers. The term albuterol commonly refers to a racemic mixture of (R)- and (S)-albuterol. Herein, the term albuterol is defined as including a racemic mixture, a single enantiomer of albuterol, or any mixture of enantiomers of albuterol. Albuterol is a xcex2-adrenergic antagonist and acts to relax smooth muscle. It is, therefore, particularly effective as a bronchodilator in the treatment of asthma. Racemic albuterol and racemic albuterol sulfate are commercially available as Proventil(copyright), Ventolin(copyright) and Vormax(copyright). The pure (R)-enantiomer, which has the generic name levalbuterol, is commercially available as Xopenex(copyright).
It is known that albuterol degrades in aqueous solution. (See, for example, U.S. Pat. No. 4,499,108, which relates to albuterol sulfate syrups that are stable upon prolonged storage.) The cause(s) and mechanisms of the degradation reaction(s) are not well understood, but it is known that albuterol aldehyde is one of the degradation products. The level of albuterol aldehyde in an albuterol formulation for inhalation is regulated by the Food and Drug Administration because of the potentially negative effects of administering an aldehyde compound to a patient by inhalation. Currently, a maximum of 0.05% by weight albuterol aldehyde is allowed in an albuterol formulation at the time of release, with a maximum of 0.08% at the end of the expiration date. Therefore, formation of albuterol aldehyde in an aqueous albuterol solution limits the shelf life of the package containing it.
One drawback of using BFS technology for formulations of albuterol is that it has been difficult to produce a packaged formulation having a long shelf life without including additives such as chelating agents, sequestering agents, antioxidants or preservatives in the formulation or storing the package at temperatures below room temperature. It is therefore an object of the invention to provide a method of maximizing the shelf life of an albuterol formulation packaged using BFS technology.
It has been surprisingly found that when nitrogen is used as the blowing or ballooning gas in a BFS process for packaging an albuterol formulation, a package having a long shelf life is obtained. In this respect, the present invention relates to a method for manufacturing a packaged albuterol formulation having a long shelf life comprising:
blowing nitrogen gas through a hollow cylinder of an oxygen-permeable plastic and molding the hollow cylinder into an oxygen-permeable container, thereby at least partially enclosing a reduced oxygen atmosphere;
filling the oxygen-permeable container with an aqueous formulation of albuterol, or a pharmaceutically acceptable salt thereof, the aqueous formulation containing less than 0.05% by weight of albuterol aldehyde and less than 1 ppm dissolved oxygen;
enclosing the oxygen-permeable container in a reduced oxygen atmosphere within an oxygen-impermeable wrapper to produce a package enclosing an atmosphere containing less than about 2% oxygen; whereby the amount of albuterol aldehyde contained in the aqueous formulation remains lower than 0.08% by weight for a period of at least 12 months at room temperature.
In another aspect, the present invention relates to stable packaged pharmaceutical formulations consisting essentially of:
albuterol or a pharmaceutically acceptable salt thereof;
sodium chloride; and
water;
the formulation having a pH of about 4, containing less than 0.08% by weight of albuterol aldehyde and less than 1 ppm dissolved oxygen, enclosed within an oxygen-permeable plastic container, and remaining at less than 0.08% by weight of albuterol aldehyde after storage at 40xc2x0 C. for six months. Preferably, the oxygen-permeable plastic container additionally encloses a gas phase comprising less than about 5% oxygen. The oxygen-permeable plastic container is preferably enclosed within a sealed wrapper comprising an oxygen-impermeable material. More preferably, the sealed wrapper additionally encloses a gas phase contained within the sealed wrapper and comprising less than about 5% oxygen.